The invention relates to a method for manufacturing a turbine engine fan casing, in particular for an aeroengine.
In such a turbine engine, the fan casing performs several functions. It defines the air inlet passage of the engine, it supports an abradable coating in register with the blade tips of the fan, it incorporates or supports a retention shield forming a trap for debris, and it supports a soundwave absorber structure for acoustic treatment at the inlet of the engine.
It is well known to make a fan casing out of fiber-matrix composite material, generally with an organic matrix. Thus, document EP 1 961 923 describes making such a casing by densifying a fiber preform that is obtained by winding superposed layers of a three-dimensional woven texture that incorporates preform portions for the retention shield and for the flanges at the upstream and downstream ends of the casing.
It is also well known to provide acoustic treatment by fastening acoustic panels on the inside face of the casing, in the downstream portion and/or in the upstream portion thereof, i.e. on one side or both sides of the abradable coating. Usually, the panels are in the form of juxtaposed sectors, each extending over a portion of the inside periphery of the casing, and the panels are fastened to the casing by means of inserts incorporated in the panels and by means of screws.
Fastening acoustic panels in that way presents several drawbacks. It requires the use of a large number of small parts (inserts and screws). In addition, repeated drilling of the composite material casing can harm the mechanical properties of the composite material.
It is also possible to envisage fastening acoustic panels to a composite material casing by means of adhesive. Nevertheless, it is difficult to avoid residual deformation of the panels, thereby degrading the profile of the air inlet passage at the inside surfaces of the juxtaposed panels.